JP5141160B2 - Joint structure of yoke and rotating shaft in steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coupling structure of a yoke with a rotary shaft in a steering device in which a universal joint for transmitting the rotation of high torque has no part where the fatigue strength is degraded. <P>SOLUTION: A yoke and a rotary shaft are coupled with each other by performing the serration fitting of a female serration of a hub to a male serration of the rotary shaft while maintaining the fastening margin when performing the serration fitting of a hub 32 of the yoke of the notched cylindrical shape with a slit 32b being formed in the axial direction and a female serration 32a being formed in an inner circumferential surface to the rotary shaft 14 having a male serration 14a in an outer circumference of an end. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a joint structure of a universal joint yoke and a rotary shaft incorporated in a steering device, and is particularly suitable for transmission of high torque rotation.

2. Description of the Related Art Conventionally, a cross joint universal joint called a cardan joint has been widely known as a universal joint that is incorporated in an automobile steering device and transmits the rotation of a steering shaft to a steering gear.
As shown in FIGS. 5 to 7, this cross shaft universal joint is coupled to the ends of a pair of rotary shafts 50 and 52 disposed between a steering shaft (not shown) and a steering gear (not shown). A pair of yokes 54, 56 and a cross shaft 58 that couples the pair of yokes 54, 56 so as to be swingably displaceable are provided.

  One yoke 54 has a serrated 64 a formed on the inner peripheral surface of the cylinder, and a notched cylindrical hub 64 in which a slit 64 b is formed in the axial direction of the cylinder, and a position sandwiching the slit 62 of the hub 64. A pair of flanges 66 and 68 projecting in parallel, a bolt passage hole 70 and a screw hole 72 formed at positions corresponding to each other of the pair of flanges 66 and 68, and an axis from an axial end of the hub 64 along the axis. A pair of forks 76 and 78 having a bearing hole 74 that is formed in parallel and connects the cross shaft 58 is provided.

  A serration 50a is formed on the outer periphery of the end of the rotating shaft 50 to which one yoke 54 is coupled. The hub 64 of the yoke 54 is externally fitted on the outer periphery of the end of the rotating shaft 50, and the serration 64a of the hub 64 is attached. Then, the serration 50a of the rotary shaft 50 is serrated and fitted with a gap. Then, the fastening bolt 80 inserted into the bolt passage hole 70 of one flange 66 is screwed into the screw hole 72 of the other flange 68 and fastened to bring the pair of flanges 66 and 68 close to each other, and the serration 50a and the serration 64a. The yoke 54 is coupled to the rotary shaft 50 by reducing the inner diameter of the hub 64 so as to be in close contact with each other. The other yoke 56 is also coupled to the rotary shaft 52 with the same structure.

By the way, in recent years, a steering device including an electric power steering device that transmits a steering assist force to a steering gear has been developed, and high torque rotation is transmitted also to a steering shaft and a transmission path of the steering gear of the steering device. Therefore, the universal joint is required to have a strength capable of withstanding high torque rotation.
Here, when the fastening bolt 80 is strongly fastened when the yoke 54 is coupled to the rotating shaft 50 (the yoke 56 is connected to the rotating shaft 52), the pair of flanges 66 and 68 become non-parallel and the bending load is applied to the fastening bolt 80. Therefore, as shown in FIG. 6, the fastening bolt 80 is curved.

Further, when high torque rotation is transmitted between the yoke 54 and the rotary shaft 50, as shown in FIG. 7, since the thrust load is alternately input to the pair of flanges 66 and 68, the bending load is repeatedly applied to the fastening bolt 80. Works.
Thus, the fastening bolt 80 has a bending load acting as an average stress when the yoke 54 and the rotary shaft 50 (the yoke 56 and the rotary shaft 52) are coupled, and a high torque acts as a stress amplitude during the rotation. The fatigue strength of 80 may be reduced.

Here, as a structure for preventing the strength of the fastening bolt from being lowered, for example, as shown in Patent Document 1, a nut and a bolt screw that engage with a flange from the seating surface of the head of the fastening bolt when the yoke and the rotary shaft are coupled. A technique for reducing the degree (curvature) of the fastening bolt by bending by setting the distance to the portion to a predetermined length is known.
Japanese Patent No. 3480109

However, although the technique described in Patent Document 1 reduces the degree of bending of the fastening bolt when the yoke and the rotating shaft are coupled, high torque rotation is transmitted between the yoke and the rotating shaft and between the yoke and the rotating shaft. When doing so, since a bending load always acts on the fastening bolt, it is impossible to prevent a reduction in the fatigue strength of the fastening bolt.
Therefore, the present invention has been made paying attention to the unsolved problems of the conventional example, and even when an electric power steering device that transmits a steering assist force to the steering gear is incorporated in the steering device, high torque rotation is transmitted. An object of the present invention is to provide a coupling structure of a yoke and a rotating shaft in a steering device in which a portion where the fatigue strength is reduced does not exist in the universal joint.

In order to achieve the above object, the coupling structure of the yoke and the rotating shaft in the steering device according to claim 1 is a notched cylindrical hub having a slit formed in the axial direction and a female serration formed on the inner peripheral surface; The yoke having a pair of forks formed integrally on one end side of the hub in the axial direction of the hub is coupled to the rotating shaft having a male serration formed on the outer periphery of the end portion while being serrated and fitted. In the coupling structure, the female serration of the hub is serrated and fitted with the male serration of the rotating shaft having a margin, so that the yoke and the rotating shaft are coupled, and the hub sandwiches the slit. A pair of flanges extending in parallel to each other from the position are formed, and the female serration of the hub is connected to the male selection of the rotating shaft. When serration fitted to emissions, as the inner diameter of the hub width of the slit is increased to increase, and so as to apart from each other said pair of flanges with a hub diameter means.

According to a second aspect of the present invention, in the coupling structure of the yoke and the rotating shaft in the steering device according to the first aspect , the hub diameter increasing means is provided on one of the pair of flanges and on the other inner surface of the pair of flanges. And a bolt for expanding the diameter, which is screwed into the screw hole and has a screw tip abutting against the other inner surface of the pair of flanges.
Further, the invention according to claim 3 is the coupling structure of the yoke and the rotary shaft in the steering device according to claim 1 or 2 , wherein the female serration of the hub has a serration fitting while having a margin for the male serration of the rotary shaft. And a flange restraining means for restraining the pair of flanges from moving in a direction away from each other.

Furthermore, the invention of claim 4 is the coupling structure of the yoke and the rotary shaft in the steering device according to any one of claims 1 to 3 , wherein the flange restraining means is a screw fastening member communicating with a pair of flanges. It is.

  According to the coupling structure of the yoke and the rotating shaft in the steering device of the present invention, the yoke and the rotating shaft are coupled by the serration fitting while the female serration of the hub has a margin for the male serration of the rotating shaft. As in the past, there is no need for a fastening bolt that applies a bending load to reduce the inner diameter of the hub and couple it to the rotating shaft, and a steering assist means for transmitting a steering assist force to the steering gear is incorporated in the steering device, so that high torque rotation is achieved. There is no portion where the fatigue strength is reduced even when the yoke is transmitted between the yoke and the rotating shaft, and the yoke and the output shaft can be reliably coupled.

Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.
1 to 4 are views showing a steering device according to the present invention, FIG. 1 is an overall configuration diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing a universal joint incorporated in the steering device, FIG. 3 is a cross-sectional view taken along the line BB in FIG. 2, and FIG. 4 is a view showing a state in the middle of coupling of the yoke and the rotating shaft.

Reference numeral 2 in FIG. 1 denotes a steering shaft having a steering wheel 1 mounted on the vehicle rear end (right end in FIG. 1). The steering shaft 2 is disposed with an upward inclination toward the rear of the vehicle. The column 3 is rotatably held.
On the vehicle front end (left end in FIG. 1) side of the steering shaft 2, a worm speed reducer 11 that applies steering assist torque to the steering shaft 2 and an electric motor 12 that generates steering assist torque in the worm speed reducer 11 are configured. The steering assist mechanism 4 is connected.

The steering shaft 2 has an outer shaft 7 and an inner shaft 8, and a front end portion of the outer shaft 7 and a rear end portion of the inner shaft 8 are spline-coupled.
A cylindrical steering column 3 through which the steering shaft 2 is inserted is formed by combining an outer column 9 and an inner column 10 in a telescope shape, and is fitted so that its position can be adjusted in the axial direction.

  On the vehicle front side of the outer column 9, a clamp portion (not shown) separated in the vehicle width direction that holds the outer periphery of the inner column 10 is integrally formed, and this clamp portion is fixed to the vehicle body side member 16. The upper bracket 26 is sandwiched from the vehicle width direction. The upper bracket 26 is provided with a clamp device 27 that clamps the inner column 10 via a clamp portion.

Further, the housing 11a of the worm speed reducer 11 in the steering assist mechanism 4 is supported so as to be swingable in the vertical direction around a pivot pin 24 rotatably supported by a lower bracket 23 attached to the vehicle body side member 16. ing.
Then, the front end portion of the inner column 10 is fixed to the rear end surface of the housing 11a of the worm speed reducer 11, the inner shaft 8 is inserted into the housing 11a of the worm speed reducer 11, and the front end portion of the inner shaft 8 is The speed reducer 11 is connected to an output shaft 14 protruding from the front end surface of the housing 11a.

An intermediate shaft 18 is connected to the output shaft 14 of the worm reducer 11 via a universal joint 17A, and this intermediate shaft 18 is connected to a pinion shaft 19 of a rack and pinion type steering gear mechanism 6 via a universal joint 17B. Has been. The intermediate shaft 18 employs a telescopic shaft composed of a male shaft 18a and a female shaft 18b.
Although not shown, the steering gear mechanism 6 is configured in a rack and pinion type in which a pinion connected to a pinion shaft 19 and a rack shaft having a rack meshing with the pinion are arranged in a gear housing. Rotational motion transmitted to is converted to linear motion on the rack shaft. A rack shaft (not shown) is connected to a steered wheel (not shown) via a tie rod 5.

As shown in FIG. 2, the universal joint 17A for connecting the output shaft 14 and the female shaft 18b of the intermediate shaft 18 is connected to the first yoke 30 connected to the end of the output shaft 14 and the end of the female shaft 18b. A second yoke 31 and a cross shaft 40 that couples the first and second yokes 30 and 31 so as to be swingable and displaceable are provided.
The first yoke 30 includes a notched cylindrical hub 32 and a pair of forks 33 and 34 formed in parallel from the axial end of the hub 32 along the axis.

As shown in FIG. 3, the hub 32 has a female serration 32a on the inner peripheral surface and a slit 32b in the axial direction. The hub 32 is formed with a pair of flanges 35 and 36 so as to be parallel to each other from a position sandwiching the slit 32b.
A first screw hole 37 penetrating toward the other flange 36 is formed in one flange 35, and an inner surface corresponding to the first screw hole 37 of the other flange 36 is a flat surface.

One flange 35 is formed with a bolt passage hole (not shown) toward the other flange 36, and the other flange 36 has a second screw hole (not shown) at a position facing the bolt passage hole. ) Is formed.
Further, as shown in FIG. 3, a male serration 14a is formed on the outer periphery of the end of the output shaft 14, and the hub 32 of the first yoke 30 is externally fitted on the outer periphery of the end of the output shaft 14. A female serration 32a formed on the inner peripheral surface of 32 and a male serration 14a of the output shaft 14 are serrated.

Here, the outer diameter dimension of the male serration 14 a of the output shaft 14 is slightly larger than the inner diameter dimension of the female serration 32 a of the hub 32, and the inner diameter dimension of the male serration 14 a of the output shaft 14 is the outer diameter dimension of the female serration 32 a of the hub 32. It is set slightly larger.
Further, one flange 35 is formed with a bolt passage hole (not shown) toward the other flange 36, and the other flange 36 has a second screw hole (not shown) at a position facing the bolt passage hole. ) And a bolt 38 inserted into a bolt passage hole of one flange 35 is screwed into a screw hole of the other flange 36.
The second yoke 31 coupled to the end of the female shaft 18b is also coupled with the same structure as the first yoke 30 coupled to the end of the output shaft 14 described above.

Next, a procedure for coupling the first yoke 30 to the output shaft 14 will be described with reference to FIGS.
A diameter expansion bolt 39 is screwed into a first screw hole 37 formed in one flange 35 of the hub 32, and a screw tip 39 a of the diameter expansion bolt 39 is brought into contact with the inner surface of the other flange 36. Then, the screwing amount of the diameter expansion bolt 39 is increased, and the screw tip 39a presses the other flange 36, whereby the hub 32 is elastically formed so that the width of the slit 32b is increased as shown in FIG. Let's transform.

  Then, the end of the output shaft 14 is placed in the hub 32 which is elastically deformed with the width of the slit 32b increased so that the inner diameter of the female serration 32a is larger than the outer diameter of the male serration 14a of the output shaft 14. insert.

Next, the screwing amount of the diameter-expansion bolt 39 into the first screw hole 37 is decreased, and the hub 32 is elastically returned so that the width of the slit 32b is restored.
At this time, the outer diameter dimension of the male serration 14a of the output shaft 14 is slightly larger than the inner diameter dimension of the female serration 32a of the hub 32, and the inner diameter dimension of the male serration 14a is set slightly larger than the outer diameter dimension of the female serration 32a. Therefore, the female serration 32a of the hub 32 that has returned elastically is serrated and fitted to the male serration 14a of the output shaft 14 with a tightening margin, whereby the first yoke 30 is coupled to the output shaft 14.

Then, the retaining bolt 38 inserted into the bolt passage hole of one flange 35 is screwed into the screw hole of the other flange 36, and the pair of flanges 35, 36 are fastened.
The second yoke 31 is also coupled to the female shaft 18b in the same procedure as the coupling of the first yoke 30 and the output shaft 14.
Here, the hub diameter increasing means of the present invention corresponds to the first screw hole 37 and the bolt 39 for diameter expansion, the screw hole of the present invention corresponds to the first screw hole 37, and the screw fastening member of the present invention is prevented from coming off. It corresponds to the bolt 38.

Next, the effect of this embodiment will be described.
In the prior art shown in FIGS. 5 to 7, the yoke 54 is coupled to the rotary shaft 50 by using a fastening bolt 80 that reduces the inner diameter of the hub 64 by bringing a pair of flanges 66 and 68 close to each other. It was.
However, in the present embodiment, the female serration 32a of the hub 32 of the first yoke 30 is serrated and fitted to the male serration 14a of the output shaft 14 with a tightening margin, so that the first yoke 30 is connected to the output shaft 14. The fastening bolt 80 used in the prior art is not used.

Here, in the retaining bolt 38 of the present embodiment, when rotation is transmitted between the first yoke 30 and the output shaft 14, the pair of flanges 35 and 36 are separated from each other, and the hub 32 is expanded in diameter. These are bolts that prevent the output shaft 14 from coming off.
For this reason, the retaining bolt 38 is not subjected to a bending load when the first yoke 30 is coupled to the output shaft 14, and a pair of high-torque rotations are input from the steering assist mechanism 4 to the output shaft 14. Since the bending load is only repeatedly applied by the thrust load input to the flanges 35 and 36, the fatigue strength of the retaining bolt 38 does not decrease.

Therefore, in the present embodiment, even if the steering assist mechanism 4 that transmits the steering assist force to the steering gear mechanism 6 is incorporated in the steering device, there is no portion where the fatigue strength is reduced in the universal joint 17A that transmits the high torque rotation. In addition, the first yoke and the output shaft 14 can be reliably coupled.
Further, in the present embodiment, the screw tip 39a presses the other flange 36 by increasing the screwing amount of the diameter expanding bolt 39 screwed into the first screw hole 37 of one flange 35 of the hub 32, and the slit The end of the output shaft 14 is inserted by elastically deforming the hub 32 so as to increase the width of 32b, the screwing amount of the bolt 39 for expanding the diameter into the first screw hole 37 is reduced, and the width of the slit 32b is based on Since the first yoke 30 is coupled to the output shaft 14 by elastically returning the hub 32 so as to return, the coupling operation of the first yoke 30 and the output shaft 14 can be easily performed.

Further, since the second yoke 31 is also coupled to the female shaft 18b in the same procedure as the coupling of the first yoke 30 and the output shaft 14, the same effect as the coupling structure of the first yoke 30 and the output shaft 14 is obtained. A coupling structure of the second yoke 31 and the female shaft 18b can also be obtained.
The same effect can be obtained if the universal joint 17B that connects the male shaft 18a of the intermediate shaft 18 and the pinion shaft 19 of the steering gear mechanism 6 has the same coupling structure as the above-described universal joint 17A.

  In the above embodiment, the diameter-expanding bolt 39 is screwed into the first screw hole 37 formed in one flange 35 of the hub 32, and the screw tip 39 a of the diameter-expanding bolt 39 is connected to the other flange 36. The first screw hole 37 is formed in the other flange 36, and the diameter-expanding bolt 39 screwed into the first screw hole 37 is brought into contact with the inner surface of one flange 35. You may do it.

1 is a configuration diagram illustrating an entire steering apparatus according to the present invention. It is a figure which shows the universal joint integrated in the steering apparatus which concerns on this invention. It is a BB arrow sectional view of Drawing 2. It is a figure which shows the state in the middle of the coupling | bonding of a yoke and a rotating shaft. It is a figure which shows the conventional universal joint integrated in the steering apparatus. It is an AA arrow directional view of FIG. It is a figure which shows the external force input into a yoke when rotation of a high torque is transmitted to the conventional universal joint.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Steering wheel, 2 ... Steering shaft, 3 ... Steering column, 4 ... Steering assistance mechanism, 5 ... Tie rod, 6 ... Steering gear mechanism, 7 ... Outer shaft, 8 ... Inner shaft, 9 ... Outer column, 10 ... Inner column 11 ... Worm reducer, 11a ... Housing, 12 ... Electric motor, 14 ... Output shaft, 14a ... Male serration, 16 ... Body member, 17A ... Universal joint, 17B ... Universal joint, 18 ... Intermediate shaft, 18a ... Male Shaft, 18b ... Female shaft, 19 ... Pinion shaft, 23 ... Lower bracket, 24 ... Pivot pin, 26 ... Upper bracket, 27 ... Clamp device, 30 ... First yoke, 31 ... Second yoke, 32 ... Hub, 32a ... Female serration, 32b ... slit, 33, 34 ... fork, 35, 36 ... flange, 37 ... first screw , 38 ... retaining bolt, 39 ... diameter bolts, 39a ... tip of the enlarged diameter bolt, 40 ... cross shaft

Claims (4)

A yoke including a notched cylindrical hub having a slit formed in the axial direction and a female serration on the inner peripheral surface and a pair of forks formed integrally on one end side in the axial direction of the hub In the coupling structure of the yoke and the rotating shaft in the steering device that is coupled while being serrated to the rotating shaft formed with the male serration on the outer periphery,
While the female serration of the hub is serrated to fit the male serration of the rotating shaft with a margin, the yoke and the rotating shaft are coupled ,
The hub is formed with a pair of flanges extending parallel to each other from a position sandwiching the slit, and when the female serration of the hub is serrated to the male serration of the rotating shaft, the width of the slit A yoke and a rotating shaft coupling structure in a steering device, wherein the pair of flanges are separated from each other by using hub diameter increasing means so that the inner diameter of the hub is increased by increasing the inner diameter of the hub . The hub diameter-expanding means includes a screw hole that penetrates one of the pair of flanges toward the other inner surface of the pair of flanges, and is screwed into the screw hole, and a screw tip is the other inner surface of the pair of flanges. 2. A coupling structure for a yoke and a rotary shaft in a steering apparatus according to claim 1 , wherein the structure is composed of a diameter-expanding bolt abutting against the steering wheel. And a flange restraining means for restraining the pair of flanges from moving away from each other when the female serration of the hub is serrated with the male serration of the rotating shaft having a margin. 3. A coupling structure of a yoke and a rotary shaft in a steering device according to claim 1 or 2 . Said flange restraining means, coupling structure of the yoke and the rotating shaft in the steering device according to any one of claims 1 to 3, characterized in that a screw fastening member communicating with the pair of flanges.

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